the mashup pack seems to not play certain soundtracks at all no matter where you go 

(i do not know the names of the soundtracks but i can try to put them out)

the music that is supposed to play in the menu doesn't play unless you defeat the dragon

and for the nether none of the nether soundtracks play at all 

I tried using commands to play certain soundtracks but it didn't work 

in the nether I traveled to different biomes to see if the music would play but it did not 

• Halloween menu
• Halloween nether 1 
• Halloween nether 2